1. Field of the Invention
The present invention relates to white road line recognition devices for vehicles that recognize white road lines based on images captured by an onboard camera.
2. Description of the Related Art
For the improvement of vehicle safety, driving support devices have recently been developed that actively support driver's operations. In order to achieve a function such as lane deviation prevention, a driving support device generally recognizes a white road line based on a captured image in front of an own vehicle, and the like, and makes an estimation on an own lane based on the captured white road line.
There are many types of actual white road lines besides on a white road line comprised of a single lane division line, such as a double white road line having a dashed line for visual guidance or the like inside the lane division line.
Therefore, upon the recognition of the white road line of this type, it is necessary to adequately consider the visual guidance line or the like in addition to the lane division line. Japanese Unexamined Patent Application Publication No. 2007-264955 (hereunder referred to as “Patent Document 1”) discloses a technology that recognizes such a white road line. The technology first recognizes a road surface based on distance information that is obtained by processing of a pair of images. Among pixels on the recognized road surface the technology then detects a pixel whose luminance and differential value thereof are equal to or exceed a set threshold as a white road line point candidate. The technology then groups together the white road line point candidates within a certain distance. When more than a predetermined number of groups are detected and a length in the distance direction in real space of each detected group and the like falls within a predetermined value, the technology detects these groups as a dashed line put on the road surface.
However, the technology disclosed in Patent Document 1 requires an accurate value of the length of the inner visual guidance line, the interval thereof, the road width and the like, and thus a complicated calculation process.